In a basic landline telephone system, a given customer's premises are connected to a telephone company switching office by a local loop telephone line, which provides the customer's premises with connectivity to the public switched telephone network, among possibly other services. At the customer's premises, the telephone line then may then couple with a local network that connects the telephone line to numerous telephones (as well as other telephony equipment such as fax machines, DSL modems, answering machines, etc.) With this arrangement, the customer can conveniently engage in a telephone call using any of the telephones at the customer's premises.
One benefit of having numerous telephones on the customer premises network is that a user can readily transfer a call from one customer premises telephone to another. One way to do so is to simply engage a “hold” function on the telephone currently in use and then pick up the call at the other telephone. Another way to do so is to pick up the other telephone so as to join it into the existing call and to then hang up the first telephone.
In advanced PBX systems of the type commonly found in most business offices, mechanisms are also provided to facilitate transfer of a call from one telephone to another. In a PBX system, a PBX server typically connects various customer premises telephones with the public switched telephone network, through a dedicated circuit connection to each telephone or over a packet-switched network connection (in an IP PBX system). To transfer an existing call from one PBX telephone to another, a user at the first PBX telephone may engage a “transfer” function on the telephone and dial the extension of the other telephone. The PBX server may then hold the call (possibly allowing the user to hang up the first telephone) and may connect the call to the other telephone when a user answers the other telephone.
Alternatively, a PBX system may provide a “pick” function that allows call transfer at the request of the target telephone. In particular, a user of one telephone may place a call on hold, and a user of another telephone may then pick up that call by engaging a “pick” function and dialing the extension of the first telephone. The pick function makes it easy for a user to move from one telephone to another, by putting the call on hold at the first telephone and then moving to the other telephone and picking up the call at the other telephone.